Aortic aneurysm. An aortic aneurysm forms in your aorta, a major blood vessel about the size of a garden hose. Your aorta carries blood from your heart to your vital organs. You may not know you have an aneurysm because they usually don't cause symptoms, even when they are large. However, an aneurysm can burst (rupture) or split (dissect), causing internal bleeding and often leading to death.

Abdominal aortic aneurysms form along the aorta in the section that passes through your abdomen. Thoracic aortic aneurysms form along the aorta in the section that passes through your chest area. Thoracoabdominal aortic aneurysms form along the section of the aorta between your chest area and abdomen.

Brain aneurysm. A brain aneurysm occurs in a blood vessel supplying your brain, usually at branching points of arteries. The weakened area forms a small sac or balloon that fills with blood. Brain aneurysms can rupture and cause bleeding into your brain, resulting in a subarachnoid hemorrhage.

Some small brain aneurysms, especially those located on the arteries in the front part of your brain, have a low risk of rupture. Doctors will assess the size, location and appearance of the aneurysm to clarify the risk of rupture. Medical and family history also can help clarify the risk. Doctors will then compare that risk to the risk of treatment and decide whether to manage or treat the aneurysm.

Peripheral aneurysm. A peripheral aneurysm forms in other blood vessels in your body, including arteries in your legs, groin or neck.

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